In recent years, luminescence devices, such as field emission devices, have received much attentions, due to they have the advantages of low operating voltage, little power consumption, no need of deflection coil, no X-ray radiation, anti-interference ability of radiation and magnetic field. The combination of field emission cathodes and luminescent material can provide field emission light source with high brightness and high color rendering, which can be applied in the fields such as displaying, various indicating and general lighting. The working principle of the field emission devices is similar to that of the traditional cathode ray tube (CRT), specifically, the application of imaging or lighting are realized by bombardment of electron beam to trichromatic fluorescence powder of red, green and blue. The field emission devices have potential advantages in the aspects such as brightness, viewing angle, response time, range of operating temperature and energy consumption.
The germanate luminescent material doped with rare earth ion has good photoluminescence properties, and could emit light with high fluorescence color and high brightness after been excitated, thus could be applied as trichromatic fluorescence of UV-LED. However, further improves the luminescence properties of the materials has been the targets of the researchers. One of the key factors of the preparation of field emission devices with excellent properties is the preparation of fluorescence powder with excellent properties. Currently, the fluorescence materials used in field emission devices mainly are the fluorescence powder of series sulfide, series oxide and series oxysulfide used in traditional cathode ray tube and projection television tubes. The fluorescence powder of series sulfide and series oxide have high brightness and certain electrical conductivity, while, these fluorescence powder are prone to be decomposed under the bombardment of large electron beam, could produce sulfur to poison the cathode tip, and could generate other sediment covering the fluorescence powder surface, thus reducing the luminescence efficiency of the fluorescence powder and decreasing the lifetime of the field emission devices. The fluorescence powder of series oxide have good stability, while their luminescence efficiency are not high enough, and they are generally made from insulators materials, both of the disadvantages are to be improved and enhanced.